Elastic-plastic Solution Of TBM Inclined Shaft Surrounding Rocks Based On Unified Strength Criterion And Test Research

In recent years,with the developing of coal mining technology,coal mining depth is increasing,and coal mine production capacity continues to grow.There are a variety of problems encountered in the process of mining.The inclined shaft development becomes the main method of improving the productivity.TBM construction has become an important means of inclined shaft construction with its advantages such as high efficiency,high quality and safety.It is a major challenge to carry out the TBM inclined shaft construction in the complicated conditions like long distance and large depth in the coal mine construction in China.There are many unpredictable problems in the construction process.It is important to study the stability of surrounding rocks and the stresses condition of supporting structures to engineering safety evaluation.But the related research results are less,which is the urgent problem to be solved.In this thesis,according to the problems such as large slopes,large depths and driving in complex strata in the construction of TBM inclined shaft,this paper takes the project of Shenhua Taigemiao TBM construction inclined-shaft as the basis.The paper makes a systematic study of surrounding rocks mechanical properties considering the interaction between surrounding rocks and supporting structures.Methods like theory analysis,model test and numerical simulation are used during the study.In the rich water strata,the seepage force of groundwater should be taken into account,the paper also makes a mechanical analysis and theoretical study of surrounding rocks in this condition.The main research contents are as follows:(1)Elastic-plastic theoretical study of surrounding rocks of TBM inclined shaft based on unified strength criterionBased on the theory of coordinate transformation,the elastic-plastic mechanics analysis model of TBM inclined shaft is established.Based on the unified strength criterion,the analytical formulas of plastic radius,stresses and displacements of surrounding rocks are deduced under two-dimension unequal pressure.The calculation and parametric analysis is performed combined with the actual survey dates in the project of Shenhua Taigemiao TBM construction inclined-shaft.The influences of the intermediate principal stress parameter,the inclination of inclined shaft,the pressure coefficient and the elastic modulus ratio of the lining and the surrounding rock on the plastic radius,the stresses of surrounding rocks and the radial displacements in the plastic zone are thoroughly researched.The results show that the stability of surrounding rocks can be improved by considering the effects of intermediate principal stress.Plastic radius,the surrounding rock stresses and displacements are influenced by lateral pressure coefficient,inclined shaft angle and the elastic modulus ratio of the lining and the surrounding rock differently.And the greater the elastic modulus ratio of the lining and the surrounding rock,the greater the lining support forces.The research results provide theoretical basis for the construction and safety evaluation of TBM inclined shaft under similar conditions,and can be referenced by similar projects.(2)The elastic-plastic analytical solution of TBM inclined shaft surrounding rocks considering the seepage effectThe stress field-seepage field coupling analysis of the TBM inclined shaft is carried out considering the interaction between supporting and surrounding rocks.The elasticplastic mechanics model of the TBM inclined shaft cross section is established.Based on unified strength criterion and a non-associated flow rule,the elastic-plastic solution of TBM inclined shaft surrounding rocks is derived considering the seepage force and dilatancy angle.The effects of seepage force and dilatancy angle on plastic radius,stresses and displacements of surrounding rocks are studied deeply.The results show that the effects of seepage force on mechanical properties of surrounding rocks should not be ignorable.The greater the hydraulic press ration between inside and outside the pores,the more obvious the effects of seepage force are.The plastic radius and displacement of surrounding rocks in plastic region are significantly affected by dilatancy angle,which has little effects on stresses of surrounding rocks.(3)Numerical simulation of the variation of stresses and displacement of TBM inclined shaft surrounding rocksThe surrounding rocks and lining of TBM inclined shaft under different depth are simulated by the FLAC3 D numerical calculation software.The changing laws of the plastic region,the stresses and displacement in surrounding rocks with depth,lateral pressure coefficient,inclination angle,and the elastic modulus ratio of the lining and the surrounding rock are achieved.The stresses and displacements distribution in the cross section of the inclined shaft is achieved by slicing the numerical calculation model,and the numerical calculation results are compared with theoretical calculation results,which are verified well.The results of numerical simulation show highly consistent with the theoretical calculation.(4)Model testing research of surrounding rocks displacement and lining internal force changingThe inclined shaft depth was simulated by vertical step by step loading method.The mechanical properties of surrounding rocks and segments under different loads are studied through the laboratory model test.The variation law of radial displacement,internal forces in different position of segments with the variation of vertical loading are achieved.The influences of different material segments structure on the displacement of surrounding rocks and the variation of its own internal forces are achieved by using different materials to make the lining structure.The experimental results are compared with the theoretical results in the thesis.The results show that with the increase of the vertical loading,the radial displacement of surrounding rocks gradually increases,and the displacement of surrounding rocks in vertical direction is obviously larger than that in horizontal direction.The plastic zone in horizontal direction and vertical direction are different.Both axial force and bending moment of segments increase with the increasing of loading.The axial force is pressure force,and the maximum axial force is at the side waist of segments,the minimum axial force is at the top.The bending moments at the top and bottom of segments were positive,while at the side waist were negative.The simulation results show the same variation law.The joint position less affected the axial force and bending moment.In actual engineering,the strength and rigidity of the segment structure should be strengthened and readjusted according the change of inclined shaft depth to satisfy the need of engineering.